Semiconductor device

ABSTRACT

The semiconductor device according to the present invention includes a semiconductor substrate, a first insulating layer laminated on the semiconductor substrate, a first metal wiring pattern embedded in a wire-forming region of the first insulating layer, a second insulating layer laminated on the first insulating layer, a second metal wiring pattern embedded in a wire-forming region of the second insulating layer and first dummy metal patterns embedded each in a wire-opposed region opposing to the wire-forming region of the second insulating layer and in a non-wire-opposed region opposing to a non-wire-forming region other than the wire-forming region of the second insulating layer, the wire-opposed region and the non-wire-opposed region each in a non-wire-forming region other than the wire-forming region of the first insulating layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/979,728, filed Nov. 7, 2007. Further, this application claims thebenefit of priority of Japanese applications serial number 2006-302982,filed Nov. 8, 2006 and serial number 2006-306998, filed Nov. 13, 2006.The disclosures of these prior U.S. and Japanese applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device, and morespecifically, it relates to a semiconductor device having damascenewires.

2. Description of Related Art

With the recent integration of a semiconductor device, refinement ofwires is required. In order to satisfy this requirement, employment ofcopper (Cu) wires or the like having small electrical resistance inplace of conventional aluminum (Al) wires or the like is studied.

The damascene process is known as a method of forming fine copper wires.

In the damascene process, a first insulating layer is first laminated ona semiconductor substrate. Then, a first wiring trench is formed in aprescribed wire-forming region of the first insulating layer. Then, acopper film filling up the first wiring trench is formed on the firstinsulating layer. Then, the copper film is polished by chemicalmechanical polishing (CMP) for removing excess copper not embedded inthe first wiring trench, thereby forming a first copper wire embedded inthe first wiring trench. Thereafter a second insulating is laminated onthe first insulating layer, and a via hole reaching the first copperwire is formed in the second insulating layer. Further, a thirdinsulating layer is laminated on the second insulating layer formed withthe via hole. Then, a second wiring trench communicating with the viahole is formed in a prescribed wire-forming region of the thirdinsulating layer. A copper film is formed on the third insulating layer,embedded in the second wiring trench and polished by CMP, therebyforming a second copper wire electrically connected with the firstcopper wire through the via hole.

In the polishing by CMP (hereinafter simply referred to as “CMPtreatment”), however, the polishing rates for the copper films and theinsulating layers are different from each other. When the insulatinglayers are dispersed in wiring density, therefore, the surfaces of thecopper wires and the insulating layers are partially not planarized, buteasily indented by the so-called dishing. Particularly when a multilevelinterconnection structure is formed by laminating a plurality ofinsulating layers, such dishing is caused in the respective insulatinglayers, leading to remarkable indentations on the surfaces of copperwires and the insulating layers in upper layers. This may result invarious inconveniences such as dispersion in wiring resistance,defective resolution in photolithography and a short circuit between therespective wires. Such inconveniences cause reduction of the yield inthe manufacturing steps and reduction of the reliability in quality ofthe semiconductor device.

Therefore, a technique has been proposed to embed dummy wires notelectrically connected with the copper wires in the respectiveinsulating layers on non-wire-forming regions other than thewire-forming regions formed with the copper wires (refer to JapaneseUnexamined Patent Publication No. 2004-153015, for example). Thus,apparent wiring density in the respective insulating layers can be madeuniform, and dishing can be suppressed in the CMP treatment.

In the structure according to the above-mentioned proposal, however, thenon-wire-forming regions of the respective layers are set to completelycoincide with one another in plan view. Even if any of the wire-formingregions includes a portion provided with no wire, no dummy wire isformed on this portion. Therefore, a layer still dispersed in wiringdensity may remain to be dished out by the CMP treatment.

In general, a bonding pad made of a metal is laminated on the surface ofa semiconductor device for electrically connecting the semiconductordevice with an external device. A plurality of wiring layers havingwiring patterns are laminated under the bonding pad. The wiring patternsof the respective wiring layers are electrically connected with oneanother through connecting vias. The wiring pattern of the uppermostwiring layer is electrically connected with the bonding pad through thecorresponding connecting via. The wiring pattern of the uppermost wiringlayer is further electrically connected with an element built on asemiconductor substrate for the semiconductor device. The bonding padand a lead electrode (external electrode) of a lead frame are connectedwith each other by a bonding wire formed by a gold thin wire, therebyattaining electrical connection between the semiconductor device(element built on the semiconductor substrate) and the lead frame.

According to another method employing the damascene process, a first viahole reaching a semiconductor substrate is first formed in a firstinsulating layer made of silicon oxide (SiO₂) formed on thesemiconductor substrate. Then, a first wiring trench is formed in thefirst insulating layer formed with the first via hole. Thereafter, acopper film is formed on the first insulating layer to fill up the firstvia hole and the first wiring trench. Then, the copper film is polishedby chemical mechanical polishing (CMP) for removing excess copper notembedded in the first wiring trench, thereby forming a first copper wireembedded in the first wiring trench.

Then, a second insulating layer is formed on the first insulating layer,and a second via hole reaching the first copper wire is formed in thesecond insulating layer. A second wiring trench corresponding to thepattern of a bonding pad is formed in the second insulating layer formedwith the second via hole, and copper is embedded in the second via holeand the second wiring trench, thereby forming a second copper wireelectrically connected with the first copper wire.

Further, a third insulating layer is formed on the second insulatinglayer, and a third via hole reaching the second copper wire is formed inthe third insulating layer. A pad trench for embedding the bonding padis formed in the third insulating layer, and copper is embedded in thethird via hole and the pad trench by a method similar to that in thecases of the first and second copper wires, thereby forming the bondingpad electrically connected with the second copper wire.

However, the bonding pad is generally in the form of a rectangle (100 μmsquare, for example) having a relatively large area. If each pattern ofthe copper wires includes a pattern of the same shape opposite to thebonding pad, therefore, this pattern also has a relatively large area,similarly to the bonding pad. When copper films not embedded in therespective wiring trenches are polished by the CMP treatment, therefore,the surfaces of the copper wires are not planarized but easily indentedby dishing. Particularly when a multilevel interconnection structure isformed by laminating a plurality of wiring layers, such dishing iscaused in each of the wiring layers, leading to a remarkable indentationin the upper layer. This may result in various inconveniences such asdefective resolution in photolithography and a short circuit between therespective wiring layers.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor devicecapable of preventing dishing resulting from CMP treatment.

A semiconductor device according to one aspect of the present inventionincludes: a semiconductor substrate; a first insulating layer laminatedon the semiconductor substrate; a first metal wiring pattern embedded ina wire-forming region of the first insulating layer; a second insulatinglayer laminated on the first insulating layer; a second metal wiringpattern embedded in a wire-forming region of the second insulatinglayer; and first dummy metal patterns embedded each in a wire-opposedregion opposing to the wire-forming region of the second insulatinglayer and in a non-wire-opposed region opposing to a non-wire-formingregion other than the wire-forming region of the second insulatinglayer, the wire-opposed region and the non-wire-opposed region each in anon-wire-forming region other than the wire-forming region of the firstinsulating layer.

According to this structure, the first metal wiring pattern is embeddedin the wire-forming region of the first insulating layer laminated onthe semiconductor substrate. The second metal wiring pattern is embeddedin the wire-forming region of the second insulating layer laminated onthe first insulating layer. The first dummy metal patterns embedded eachin a wire-opposed region opposing to the wire-forming region of thesecond insulating layer and in a non-wire-opposed region opposing to anon-wire-forming region other than the wire-forming region of the secondinsulating layer, wherein the wire-opposed region and thenon-wire-opposed region each are in a non-wire-forming region other thanthe wire-forming region of the first insulating layer.

In other words, in the first insulating layer, the first dummy metalpatterns are formed not only in the non-wire-opposed region opposed tothe non-wire-forming region of the second insulating layer but also inthe wire-opposed region opposed to the wire-forming region of the secondinsulating layer. Thus, patterns constituted of the first metal wiringpattern and the first dummy metal patterns are uniformly arranged on theentire first insulating layer, whereby dispersion in pattern density(wiring density) can be reduced in the first insulating layer.

In CMP treatment for embedding the first metal wiring pattern and thefirst dummy metal patterns in the first insulating layer, therefore,dishing can be suppressed. Consequently, inconveniences such asdispersion in wiring resistance, defective resolution inphotolithography and a short circuit between respective wiring layerscan be suppressed.

Preferably, the semiconductor device further includes a second dummymetal pattern embedded in the non-wire-forming region of the secondinsulating layer, and a via connecting the first dummy metal patternembedded in the non-wire-opposed region of the first insulating layerand the second dummy metal pattern with each other.

According to this structure, the second dummy metal pattern embedded inthe non-wire-forming region of the second insulating layer and the firstdummy metal pattern embedded in the non-wire-opposed region of the firstinsulating layer are connected with each other through the via.

With application of damascene wires to a semiconductor device, capacity(parasitic capacity) may be formed between wires of respective layers.Therefore, a technique has been studied to form first and secondinsulating layers using a low dielectric constant material (having adielectric constant k of not more than 3.5, for example) in place ofconventionally used silicon oxide (SiO₂). However, low dielectricconstant films are so inferior in mechanical strength to silicon oxidefilms that the first and second insulating layers may be stripped fromeach other or the respective insulating layers may be cracked due tostress applied to the interface between the first and second layers orthe interiors of the respective insulating layers in the CMP treatment.

According to the structure connecting the first and second dummy metalpatterns with each other through the via, the via functions as a metalpost passing through the second insulating layer, whereby the secondinsulating layer can be prevented from remarkable cracking, and theadhesiveness between the first and second insulating layers can beimproved. Consequently, even if low dielectric constant films are usedfor the insulating layers, it is possible to prevent stripping andcracking of the insulating layers.

Preferably in the semiconductor device, the first dummy metal patternsand the second dummy metal pattern are each arranged in a staggeredmanner.

According to this structure, the first and second dummy metal patternsare each arranged in a staggered manner. In other words, the dummy metalpatterns and the insulating layers are alternately adjacently arrangedon the surfaces of the non-wire-forming regions of the respectiveinsulating layers. Even if the surface of any of the insulating layersis cracked, therefore, the dummy metal pattern adjacent thereto can stopthis cracking, whereby the insulating layer can be prevented fromremarkable (long) cracks.

A semiconductor device according to another aspect of the presentinvention includes: a semiconductor substrate; a wiring layer laminatedon the semiconductor substrate; a surface insulating layer laminated onthe wiring layer; and a bonding pad embedded in a surface of the surfaceinsulating layer and connected with a bonding wire for externalelectrical connection, wherein the wiring layer includes: an insulatinglayer; a residual insulating layer portion formed by partially leavingthe insulating layer in a wiring trench formed by digging down theinsulating layer; and a metal wiring pattern formed by embedding ametallic material in the wiring trench and electrically connected withthe bonding pad.

According to this structure, the wiring layer formed under the surfaceinsulating layer formed with the bonding pad includes the insulatinglayer, the residual insulating layer portion formed by partially leavingthe insulating layer in the wiring trench formed by digging down theinsulating layer and the metal wiring pattern formed by embedding themetallic material in the wiring trench and electrically connected withthe bonding pad.

Thus, the residual insulating layer portion is formed in the wiringtrench of the insulating layer, whereby the width of the metal wiringpattern formed by embedding the metallic material in the wiring trenchcan be relatively reduced. Therefore, the surface area of the metalwiring pattern can be reduced as compared with a metal wiring patternformed by filling up the wiring trench with copper without providing theresidual insulating layer portion in the wiring trench. When themetallic material is deposited on the insulating layer formed with thewiring trench and the residual insulating layer portion, and a part ofthe metallic material overflowing the wiring trench is polished by theCMP treatment, therefore, the metal wire can be prevented from dishing.Consequently, defective resolution in photolithography and a shortcircuit between the respective wiring layers can be suppressed, and asemiconductor device having high reliability in quality can be obtained.

Preferably, the wiring layer includes at least first and second wiringlayers. In this case, the semiconductor device preferably furtherincludes a bonding pad connecting via formed through the surfaceinsulating layer for connecting the metal wire of the first wiring layerand the bonding pad with each other, and a metal wire connecting viaformed through the insulating layer of the first wiring layer forconnecting the metal wire of the first wiring layer and the metal wireof the second wiring layer with each other. The bonding pad connectingvia and the metal wire connecting via are so formed that the bondingpad, the first wiring layer and the second wiring layer can beelectrically connected with one another.

Preferably, the bonding pad connecting via and the metal wire connectingvia are so formed that positions in a direction parallel to a surface ofthe semiconductor substrate deviate from each other. Thus, the bondingpad connecting via and the metal wire connecting via connecting thecontinuous and individual layers with one another are not aligned witheach other, but the positions thereof deviate from each other in thevertical direction, whereby stress applied to the bonding pad inconnection with the bonding wire, formation of a bump or probing for adevice test can be dispersed and relaxed. Consequently, the insulatinglayers can be prevented from cracking.

The above and other objects, features and effects of the presentinvention will become more apparent from the following detaileddescription of the present invention with reference to accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing the structure of asemiconductor device according to a first embodiment of the presentinvention;

FIG. 2 is a schematic plan view of a second layer shown in FIG. 1, asseen from the top;

FIG. 3 is a schematic plan view showing the structure of a semiconductordevice according to a second embodiment of the present invention;

FIG. 4 is a plan view showing the circumference of each bonding padshown in FIG. 3;

FIG. 5 is a sectional view taken along the line B-B in FIG. 4; and

FIG. 6 is a schematic sectional view showing a modification of thesemiconductor device shown in FIG. 3 in which a bonding pad is inanother structure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a schematic sectional view showing the structure of asemiconductor device according to a first embodiment of the presentinvention.

The semiconductor device 1 has a multilevel interconnection structureincluding a semiconductor substrate 2 and first, second and third layersformed by laminating these layers on the semiconductor substrate 2 inthis order.

The semiconductor substrate 2 is made of a semiconductor material suchas silicon (Si), for example, and a semiconductor element and the likeare formed on the surface layer thereof.

The first layer is formed on the semiconductor substrate 2. Morespecifically, a diffusion preventing layer 3 and an interlayer film 4are laminated on the semiconductor substrate 2 in this order, therebyforming the first layer.

The diffusion preventing film 3 is formed of silicon carbide (SiC), forexample.

The interlayer film 4 is formed using an insulating material having arelatively low dielectric constant. For example, SiOC (dielectricconstant: k=2.3 to 3.3) or SiOF (dielectric constant: k=3.3 to 3.8), forexample, is employed as such an insulating material.

The interlayer film 4 and the diffusion preventing film 3 are providedwith a wiring plug trench 5 reaching a semiconductor element region (notshown) of the semiconductor substrate 2 through these films 4 and 3.

A metallic material (copper, for example) is embedded in the wiring plugtrench 5, thereby forming a wiring plug 6. The region of the first layerformed with the wiring plug 6 is referred to as a wiring plug formingregion 40.

In a non-wiring plug forming region 41 of the interlayer film 4 and thediffusion preventing film 3 other than the wiring plug forming region40, a plurality of first dummy wiring trenches 7 (two in FIG. 1)reaching the semiconductor substrate 2 through these films 4 and 3 areformed at a prescribed interval.

A metallic material (copper, for example) is embedded in the first dummywiring trenches 7, thereby forming first dummy wires 8.

The second layer (first insulating layer) is formed on the interlayerfilm 4. More specifically, a diffusion preventing film 9, an interlayerfilm 10, a diffusion preventing film 11 and an interlayer film 12 arelaminated on the interlayer film 4 in this order, thereby forming thesecond layer.

The diffusion preventing films 9 and 11 are formed using a materialsimilar to that of the diffusion preventing film 3. The interlayer films10 and 12 are formed using a material similar to that of the interlayerfilm 4.

In the interlayer film 12 and the diffusion preventing film 11, aplurality of first wiring trenches 14 (two in FIG. 1) having aprescribed wiring pattern are formed through these films 12 and 11 at aprescribed interval.

In the interlayer film 10 and the diffusion preventing film 9, aplurality of first interwire via holes 13 communicating the first wiringtrenches 14 and the wiring plug 6 with each other are formed throughthese films 10 and 9. FIG. 1 shows only one of the plurality of firstinterwire via holes 13.

A metallic material (copper, for example) is embedded in the firstinterwire via holes 13, thereby forming first interwire vias 15. Ametallic material (copper, for example) is embedded in the first wiringtrenches 14, thereby forming first wires 16. Thus, the first wires 16are electrically connected with the wiring plug 6 through the firstinterwire vias 15.

In the second layer, the region formed with the first wires 16 and thefirst interwire vias 15 is referred to as a first wire-forming region 17(wire-forming region of the first insulating layer).

In a non-first wire-forming region 18 of the interlayer film 12 and thediffusion preventing film 11 other than the first wire-forming region17, a plurality of second dummy wiring trenches 20 (two in FIG. 1) areformed through these films 12 and 11 on positions opposed to the firstdummy wires 8 through the interlayer film 10 and the diffusionpreventing film 9 at a prescribed interval. Referring to FIG. 1, one ofthe second dummy wiring trenches 20 (closer to the first wire-formingregion 17) is referred to as a second dummy wiring trench 20A, and theother second dummy wiring trench 20 is referred to as a second dummywiring trench 20B.

In the interlayer film 10 and the diffusion preventing film 9, aplurality of first dummy via holes 19 communicating the second dummywiring trenches 20 and the first dummy wires 8 with one another areformed at a prescribed interval. Referring to FIG. 1, the first dummyvia hole 19 linked to the second dummy wiring trench 20A is referred toas a first dummy via hole 19A, and the first dummy via hole 19 linked tothe second dummy wiring trench 20B is referred to as a first dummy viahole 19B.

A metallic material (copper, for example) is embedded in the first dummyvia holes 19, thereby forming first dummy vias 21. A metallic material(copper, for example) is embedded in the second dummy wiring trenches20, thereby forming second dummy wires 22 (first dummy metal patterns).The first dummy vias 21 are so formed that the first dummy wires 8 andthe second dummy wires 22 are connected with one another.

The third layer (second insulating layer) is formed on the interlayerfilm 12. More specifically, a diffusion preventing film 23, aninterlayer film 24, a diffusion preventing film 25 and an interlayerfilm 26 are laminated on the interlayer film 12 in this order, therebyforming the third layer.

The diffusion preventing films 23 and 25 are formed using a materialsimilar to that of the diffusion preventing film 3. The interlayer films24 and 26 are formed using a material similar to that of the interlayerfilm 4.

In the interlayer film 26 and the diffusion preventing film 25, aplurality of second wiring trenches 28 (three in FIG. 1) havingprescribed wiring patterns are formed through these films 26 and 25 at aprescribed interval.

In the interlayer film 24 and the diffusion preventing film 23, aplurality of second interwire via holes 27 communicating the secondwiring trenches 28 and the first wires 16 with one another are formedthrough these films 24 and 23 at a prescribed interval. FIG. 1 showsonly two of the plurality of second interwire via holes 27.

A metallic material (copper, for example) is embedded in the secondinterwire via holes 27, thereby forming second interwire vias 29.Further, a metallic material (copper, for example) is embedded in thesecond interwire trenches 28, thereby forming second wires 30 (secondmetal wiring patterns). Thus, the second wires 30 are electricallyconnected with the first wires 16 through the second interwire vias 29.

In the third layer, the region formed with the second wires 30 and thesecond interwire vias 29 is referred to as a second wire-forming region31 (wire-forming region of the second insulating layer). In the secondlayer, a region formed with a second dummy wire 22A is referred to as afirst wire-opposed region 32 since this region is opposed to the secondwire-forming region 31. On the other hand, a region formed with seconddummy wire 22B is referred to as a first non-wire-opposed region 38since this region is opposed to a non-second wire-forming region 33outside the second wire-forming region 31.

On the non-second wire-forming region 33 of the interlayer film 26 andthe diffusion preventing film 25, a third dummy wiring trench 35 isformed through these films 26 and 25 on a position opposed to the seconddummy wire 22B through the interlayer film 24 and the diffusionpreventing film 23.

In the interlayer film 24 and the diffusion preventing film 23, aplurality of second dummy via holes 34 communicating the third dummywiring trench 35 and the second dummy wire 22B with each other areformed at a prescribed interval.

A metallic material (copper, for example) is embedded in the seconddummy via holes 34, thereby forming second dummy vias 36. A metallicmaterial (copper, for example) is embedded in the third dummy wiringtrench 35, thereby forming a third dummy wire 37 (second dummy metalpattern). The second dummy vias 36 are so formed that the second dummywire 22 and the third dummy wire 37 are connected with each other.

An insulating film 39 for preventing the second wires 30 and the thirddummy wire 37 from oxidation is formed on the interlayer film 26 so asto cover these wires 30 and 37.

FIG. 2 is a schematic plan view of the second layer of the semiconductordevice 1 shown in FIG. 1, as seen from the top. FIG. 1 corresponds to asectional view taken along the line A-A in FIG. 2.

As shown in FIG. 2, the plurality of generally rectangular second dummywires 22 (11 in FIG. 2) are arranged on the non-first wire-formingregion 18 outside the first wire-forming region 17 formed with the firstwires 16 at a prescribed interval so as to line up with one anotheralong the respective sides of the semiconductor device 1. The pluralityof second dummy wires 22 are arranged in a staggered manner as a whole,so that the dummy wires 22 of each line are not adjacent to those of theadjacent line. Due to this arrangement of the second dummy wires 22, thesurfaces of the second dummy wires 22 and the interlayer film 12alternately adjacently appear on the non-first wire-forming region 18along the respective sides of the semiconductor device 1.

Preferably, the second dummy wires 22 are so formed that the surfaceareas thereof are not less than 30% with respect to the surface area ofthe second layer. When the surface areas of the second dummy wires 22with respect to that of the second layer are within this range, dishingcan be effectively suppressed in the steps of manufacturing thesemiconductor device 1.

As shown by broken lines in FIG. 2, a plurality of second dummy vias 36(four in a set in FIG. 2) are connected to the upper surface of eachsecond dummy wire 22 (see FIG. 1). The second dummy vias 36 are arrangedon the respective corners of each second dummy wire 22 in the form of a2 by 2 matrix in plan view as a whole.

As well as on the non-wiring plug forming region 41 of the first layerof the semiconductor device 1, the first dummy wires 8 are arranged in astaggered manner as a whole similarly to the second dummy wires 22,though not shown in FIG. 2. Still further, as well as on the non-secondwire-forming region 33 of the third layer, the third metal wires 37 arearranged in a staggered manner as a whole, similarly to the second dummywires 22.

A method of manufacturing the semiconductor device 1 is now described.

In order to manufacture the semiconductor device 1, the diffusionpreventing layer 3 and the interlayer film 4 are first laminated on thesemiconductor substrate 2 in this order. Then, a photoresist (not shown)patterned correspondingly to the wiring plug trench 5 and the firstdummy wiring trenches 7 is formed on the interlayer film 4. Thisphotoresist is employed as a mask for etching the interlayer film 4 andthe diffusion preventing film 3, thereby forming the wiring plug trench5 and the first dummy wiring trenches 7 passing through the interlayerfilm 4 and the diffusion preventing film 3.

Then, the photoresist is removed, and a barrier film (not shown) isthereafter deposited by sputtering to cover the upper surface of thesemiconductor substrate 2 and the inner surfaces of the wiring plugtrench 5 and the first dummy wiring trenches 7. After this formation ofthe barrier film, a metal film (copper film, for example), not shown, isformed by electrolytic plating, sputtering or CVD, for example, to fillup the wiring plug trench 5 and the first dummy wiring trenches 7.

Then, the metal film is polished by CMP. This polishing is continueduntil the surface of the metal film is flush with that of the interlayerfilm 4, for removing excess parts of the metal film not embedded in thewiring plug trench 5 and the first dummy wiring trenches 7. At thistime, the interlayer film 4 and the wiring plug 6 can be prevented frompartial dishing, due to the first dummy wiring trenches 7 formed in theinterlayer film 4. The wiring plug 6 embedded in the wiring plug trench5 and connected to the semiconductor element region (not shown) of thesemiconductor substrate 2, and the first dummy wires 8 embedded in thefirst dummy wiring trenches 7 are formed by this polishing, forcompleting formation of the first layer.

Thereafter, the diffusion preventing film 9, the interlayer film 10, thediffusion preventing film 11 and the interlayer film 12 are laminated onthe interlayer film 4 in this order. Then, a photoresist (not shown)patterned correspondingly to the first interwire via holes 13 and thefirst dummy via holes 19 is formed. This photoresist is employed as amask for etching the interlayer film 12, the diffusion preventing film11, the interlayer film 10 and the diffusion preventing film 9, therebyforming the first interwire via holes 13 and the first dummy via holes19.

Then, a photoresist (not shown) patterned correspondingly to the firstinterwire trenches 14 and the second dummy wiring trenches 20 is formedon the interlayer film 12. This photoresist is employed as a mask foretching the interlayer film 12 and the diffusion preventing film 11,thereby forming the first interwire trenches 14 and the second dummywiring trenches 20.

Then, the photoresist is removed, and a barrier film (not shown) isdeposited by sputtering to cover the upper surfaces of the wiring plug 6and the first dummy wires 8 and the inner surfaces of the firstinterwire via holes 13, the first wiring trenches 14, the first dummyvia holes 19 and the second dummy wiring trenches 20. After thisformation of the barrier film, a metal film is formed by electrolyticplating, sputtering or CVD, for example, to fill up the first interwirevia holes 13, the first wiring trenches 14, the first dummy via holes 19and the second dummy wiring trenches 20.

Then, the metal film is polished by CMP. This polishing is continueduntil the surface of the metal film is flush with that of the interlayerfilm 12, for removing excess parts of the metal film not embedded in thefirst wiring trenches 14 and the second dummy wiring trenches 20. Atthis time, the interlayer film 12 and the first wires 16 can beprevented from partial dishing, due to the second dummy wiring trenches20 formed in the interlayer film 12. The first wires 16 embedded in thefirst wiring trenches 14 and connected with the wiring plug 6 throughthe first interwire vias 15 and the second dummy wires 22 embedded inthe second dummy wiring trenches 20 and connected with the first dummywires 8 through the first dummy vias 21 are formed by this polishing,for completing formation of the second layer.

Thereafter, the diffusion preventing film 23, the interlayer film 24,the diffusion preventing film 25 and the interlayer film 26 arelaminated on the interlayer film 12 in this order. Then, a photoresist(not shown) patterned correspondingly to the second interwire via holes27 and the second dummy via holes 34 is formed. This photoresist isemployed as a mask for etching the interlayer film 26, the diffusionpreventing film 25, the interlayer film 24 and the diffusion preventingfilm 23, thereby forming the second interwire via holes 27 and thesecond dummy via holes 34.

Then, a photoresist (not shown) patterned correspondingly to the secondwiring trenches 28 and the third dummy wiring trench 35 is formed on theinterlayer film 26. This photoresist is employed as a mask for etchingthe interlayer film 26 and the diffusion preventing film 25, therebyforming the second wiring trenches 28 and the third dummy wiring trench35.

Then, the photoresist is removed, and a barrier film (not shown) isdeposited by sputtering to cover the upper surfaces of the first wires16 and the second dummy wires 22 and the inner surfaces of the secondinterwire via holes 27, the second wiring trenches 28, the second dummyvia holes 34 and the third dummy wiring trench 35. After this formationof the barrier film, a metal film is formed by electrolytic plating,sputtering or CVD, for example, to fill up the second interwire viaholes 27, the second wiring trenches 28, the second dummy via holes 34and the third dummy wiring trench 35.

Then, the metal film is polished by CMP. This polishing is continueduntil the surface of the metal film is flush with that of the interlayerfilm 26, for removing excess parts of the metal film not embedded in thesecond wiring trenches 28 and the third dummy wiring trench 35. At thistime, the interlayer film 26 and the second wires 30 can be preventedfrom partial dishing, due to the third dummy wiring trench 35 formed inthe interlayer film 26. The second wires 30 embedded in the secondwiring trenches 28 and connected with the first wires 16 through thesecond interwire vias 29 and the third dummy wire 37 embedded in thethird dummy wiring trench 35 and connected with the second dummy wires22 through the second dummy vias 36 are formed by this polishing, forcompleting formation of the third layer.

The insulating film 39 is formed on the third layer, more specificallyon the interlayer film 26, thereby completing the semiconductor device1.

In the semiconductor device 1, as described above, the second dummywires 22 are embedded in both of the first wire-opposed region 32opposed to the second wire-forming region 31 and the firstnon-wire-opposed region 38 opposed to the non-second wire-forming region33 of the third layer in the non-first wire-forming region 18 of thesecond layer, respectively.

In other words, the second dummy wires 22 are formed not only in thefirst non-wire-opposed region 38 opposed to the non-second wire-formingregion 33 of the third layer, but also in the first wire-opposed region32 opposed to the second wire-forming region 31 of the third layer inthe second layer. Thus, patterns constituted of the first wires 16 andthe second dummy wires 22 are uniformly arranged on the entire secondlayer, whereby dispersion in pattern density (wiring density) can bereduced in the second layer.

In the CMP steps for embedding the first wires 16 and the second dummywires 22 in the second layer, therefore, dishing can be suppressed.Consequently, inconveniences such as dispersion in wiring resistance,defective resolution in photolithography and a short circuit between therespective wiring layers can be suppressed.

The third dummy wire 37 and the second dummy wires 22 embedded in thefirst non-wire-opposed region 38 are connected with each other by thesecond dummy vias 36.

With the application of damascene wires to the semiconductor device 1,capacity (parasitic capacity) may be formed between the wires of therespective layers. Therefore, a technique has been studied to form therespective interlayer films (12, 24 and 26) using a low dielectricconstant material (having a dielectric constant k of not more than 3.5)in place of conventionally used silicon oxide (SiO₂). However, lowdielectric constant films are so inferior in mechanical strength tosilicon oxide films that the second and third layers may be separatedfrom each other or the respective interlayer films (12, 24 and 26) maybe cracked due to stress applied to the interface between the second andthird layers or the interiors of the respective interlayer films (12, 24and 26) in the CMP step.

The second dummy vias 36 are so provided between the second and thirddummy wires 22 and 37 as to function as metal posts passing through theinterlayer film 24, whereby the interlayer film 24 can be prevented fromremarkable cracking and the adhesiveness between the second and thirdlayers can be improved. The interlayer films 12 and 26 can also beprevented from remarkable cracking due to the second and third dummywires 22 and 37 formed thereon, respectively. Consequently, therespective layers can be prevented from stripping and cracking even whenlow dielectric constant films are used for the interlayer films (12, 24and 26). A similar effect can also be attained between the first andsecond layers due to the first dummy vias 21 provided between the firstand second dummy wires 8 and 22.

Further, the plurality of second dummy vias 36 are arranged on therespective corners of the second dummy wires 22 in the form of 2 by 2matrices as a whole in plan view. Even if large stress is applied to thethird dummy wire 37, therefore, this stress can be uniformly dispersedto the second dummy vias 36.

In addition, the first, second and third dummy wires 8, 22 and 37 areeach arranged in a staggered manner.

In other words, the respective dummy wires (8, 22 and 37) and therespective interlayer films (4, 12 and 26) are alternately adjacentlyarranged on the non-wiring plug forming region 41 of the first layer,the non-first wire-forming region 18 of the second layer and thenon-second wire-forming region 33 of the third layer. Even if thesurface of any of the respective interlayer films (4, 12 and 26) iscracked, therefore, the respective dummy wires (8, 22 or 37) adjacentthereto can stop this cracking, whereby the respective interlayer films(4, 12 and 26) can be prevented from remarkable (long) cracks.

While the first embodiment of the present invention has been described,the present invention can also be embodied in other modes.

While the second and third layers (see FIG. 1) correspond to the firstand second insulating layers of the present invention, respectively, inthe above-mentioned first embodiment, the first and second layers (seeFIG. 1) may alternatively serve as the first and second insulatinglayers of the present invention, respectively. Further, a fourth layermay additionally be formed on the third layer, and the third and fourthlayers may serve as the first and second insulating layers of thepresent invention, respectively.

While the respective interlayer films (4, 10, 12, 24 and 26) are formedusing the low dielectric constant films made of SiOC (dielectricconstant k=2.3 to 3.3) or SiOF (dielectric constant k=3.3 to 3.8) in theabove-mentioned first embodiment, the interlayer films may alternativelybe made of conventionally used silicon oxide (SiO₂).

While the respective wires (6, 14 and 30) and the respective dummy wires(8, 22 and 37) are formed by the so-called dual damascene process in theabove-mentioned first embodiment, these wires may alternatively beformed by the so-called single damascene process.

FIG. 3 is a schematic plan view showing the structure of a semiconductordevice according to a second embodiment of the present invention.

Referring to FIG. 3, the semiconductor device 51 is generallyrectangularly formed in plan view, for example.

A plurality of bonding pads 52 (12 in this embodiment, for example) arearranged on the upper surface (surface) 51A of the semiconductor device51 along the periphery of the upper surface 51A at intervals from oneanother. Each bonding pad 52 is made of a metallic material such ascopper, aluminum or an aluminum-copper alloy, for example, and generallyrectangularly formed in plan view.

FIG. 4 is a plan view showing the circumference of each bonding pad 52shown in FIG. 3. FIG. 5 is a sectional view taken along the line B-B inFIG. 4.

The semiconductor device 51 includes a semiconductor substrate 53 aswell as a first wiring layer 54, a second wiring layer 55, a thirdwiring layer 56, a fourth wiring layer 57 and a pad layer 58successively laminated on this semiconductor substrate 53.

The semiconductor substrate 53 is made of a semiconductor material suchas silicon (Si), for example, and a functional element such as asemiconductor element is formed on the surface layer thereof.

The first wiring layer 54 is formed on the semiconductor substrate 53.The first wiring layer 54 includes an interlayer dielectric film 59laminated on the semiconductor substrate 53. The interlayer dielectricfilm 59 is made of silicon oxide, for example.

Wiring trenches 60 generally rectangular in plan view are formed in theinterlayer dielectric film 59 by digging down the interlayer dielectricfilm 59.

A plurality of residual dielectric film portions 62 (16 in thisembodiment) are formed inside the wiring trenches 60 by partiallyleaving the interlayer dielectric film 59. The residual dielectric filmportions 62 are generally rectangularly formed in plan view in a stateprotruding from the bottoms of the wiring trenches 60, and arranged inthe form of a 4 by 4 matrix in plan view as a whole (see FIG. 4).

The residual dielectric film portions 62 each are so arranged in theform of the 4 by 4 matrix as a whole that the wiring trenches 60 arearranged perpendicularly to one another at a prescribed interval to forma lattice pattern (5 by 5 in this embodiment). A metallic material(copper, for example) is embedded in the wiring trenches 60, therebyforming metal wires 61. The residual dielectric film portions 62 areexposed from the metal wires 61.

Thus, the residual dielectric film portions 62 are so provided insidethe wiring trenches 60 that the interval between the metal wires 61 canbe reduced between the interlayer dielectric film 59 and the residualdielectric film portions 62 or between the residual dielectric filmportions 62 and the residual dielectric film portions 62 in the row andcolumn directions of the wiring trenches 60.

Among the wiring trenches 60 of the lattice pattern (5 by 5) in theinterlayer dielectric film 59, the central 3 by 3 wiring trenches 60 areprovided with a plurality of substrate connecting via holes 63 passingthrough the interlayer dielectric film 59 from the bottom surfaces ofthe wiring trenches 60 and reaching the semiconductor substrate 53. Thesubstrate connecting via holes 63 are arranged in two lines on each rowand each column along the row and column directions. The wiring trenches60 and the substrate connecting via holes 63 communicate with oneanother. A metallic material (copper, for example) is embedded in thesubstrate connecting via holes 63, thereby forming substrate connectingvias 64 (see FIG. 4).

The metal wires 61 are electrically connected with the semiconductorsubstrate 53 through the substrate connecting vias 64. In other words,the first wiring layer 54 and the semiconductor substrate 53 areelectrically connected with each other.

The second wiring layer 55 is formed on the first wiring layer 54. Thesecond wiring layer 55 includes an interlayer dielectric film 65laminated on the interlayer dielectric film 59. The interlayerdielectric film 65 is made of silicon oxide, for example.

Wiring trenches 66 generally rectangular in plan view are formed in theinterlayer dielectric film 65 by digging down the interlayer dielectricfilm 65.

A plurality of residual dielectric film portions 68 (16 in thisembodiment) are formed inside the wiring trenches 66 by partiallyleaving the interlayer dielectric film 65. The residual dielectric filmportions 68 each are generally rectangularly formed in plan view in astate protruding from the bottoms of the wiring trenches 66, andarranged in the form of a 4 by 4 matrix in plan view as a whole (seeFIG. 4).

The residual dielectric film portions 68 are so arranged in the form ofthe 4 by 4 matrix as a whole that the wiring trenches 66 are arrangedperpendicularly to one another at a prescribed interval to form alattice pattern (5 by 5 in this embodiment). A metallic material(copper, for example) is embedded in the wiring trenches 66, therebyforming metal wires 67. The residual dielectric film portions 68 areexposed from the metal wires 67.

Thus, the residual dielectric film portions 68 are so provided insidethe wiring trenches 66 that the interval between the metal wires 67 canbe reduced between the interlayer dielectric film 65 and the residualdielectric film portions 68 or between the residual dielectric filmportions 68 and the residual dielectric film portions 68 in the row andcolumn directions of the wiring trenches 66.

Among the wiring trenches 66 of the lattice pattern (5 by 5) in theinterlayer dielectric film 65, the central 3 by 3 wiring trenches 66 areprovided with a plurality of interwire connecting via holes 69 passingthrough the interlayer dielectric film 65 from the bottom surfaces ofthe wiring trenches 66 and reaching the metal wires 61. The interwireconnecting via holes 69 are arranged in three lines on each row and eachcolumn along the row and column directions. Thus, the positions of thevertical central axes of the respective substrate connecting via holes63 and the central axes of the respective interwire connecting via holes69 deviate from one another in the direction parallel to the surface ofthe semiconductor substrate 53.

The wiring trenches 66 and the interwire connecting via holes 69communicate with one another. A metallic material (copper, for example)is embedded in the interwire connecting via holes 69, thereby forminginterwire connecting vias 70.

The metal wires 67 are electrically connected with the metal wires 61through the interwire connecting vias 70. In other words, the secondwiring layer 55 and the first wiring layer 54 are electrically connectedwith each other.

The third wiring layer 56 is formed on the second wiring layer 55. Thisthird wiring layer 56 includes an interlayer dielectric film 71laminated on the interlayer dielectric film 65. The interlayerdielectric film 71 is made of silicon oxide, for example.

Wiring trenches 72 generally rectangular in plan view are formed in theinterlayer dielectric film 71 by digging down the interlayer dielectricfilm 71.

A plurality of residual dielectric film portions 74 (16 in thisembodiment) are formed inside the wiring trenches 72 by partiallyleaving the interlayer dielectric film 71. The residual dielectric filmportions 74 each are generally rectangularly formed in plan view in astate protruding from the bottoms of the wiring trenches 72, andarranged in the form of a 4 by 4 matrix in plan view as a whole (seeFIG. 4).

The residual dielectric film portions 74 are so arranged in the form ofthe 4 by 4 matrix as a whole that the wiring trenches 72 are arrangedperpendicularly to one another at a prescribed interval to form alattice pattern (5 by 5 in this embodiment). A metallic material(copper, for example) is embedded in the wiring trenches 72, therebyforming metal wires 73. The residual dielectric film portions 74 areexposed from the metal wires 73.

Thus, the residual dielectric film portions 74 are so provided insidethe wiring trenches 72 that the interval between the metal wires 73 canbe reduced between the interlayer dielectric film 71 and the residualdielectric film portions 74 or between the residual dielectric filmportions 74 and the residual dielectric film portions 74 in the row andcolumn directions of the wiring trenches 72.

Among the wiring trenches 72 of the lattice pattern (5 by 5) in theinterlayer dielectric film 71, the central 3 by 3 wiring trenches 72 areprovided with a plurality of interwire connecting via holes 75 passingthrough the interlayer dielectric film 71 from the bottom surfaces ofthe wiring trenches 72 and reaching the metal wires 67. The interwireconnecting via holes 75 are arranged in two lines on each row and eachcolumn along the row and column directions. Thus, the positions of thevertical central axes of the respective interwire connecting via holes69 and the central axes of the respective interwire connecting via holes75 deviate from one another in the direction parallel to the surface ofthe semiconductor substrate 53.

The wiring trenches 72 and the interwire connecting via holes 75communicate with one another. A metallic material (copper, for example)is embedded in the interwire connecting via holes 75, thereby forminginterwire connecting vias 76 (see FIG. 4).

The metal wires 73 are electrically connected with the metal wires 67through the interwire connecting vias 76. In other words, the thirdwiring layer 56 and the second wiring layer 55 are electricallyconnected with each other.

The fourth wiring layer 57 is formed on the third wiring layer 56. Thisfourth wiring layer 57 includes an interlayer dielectric film 77laminated on the interlayer dielectric film 71. The interlayerdielectric film 77 is made of silicon oxide, for example.

Wiring trenches 78 generally rectangular in plan view are formed in theinterlayer dielectric film 77 by digging down the interlayer dielectricfilm 77.

A plurality of residual dielectric film portions 80 (16 in thisembodiment) are formed inside the wiring trenches, 78 by partiallyleaving the interlayer dielectric film 77. The residual dielectric filmportions 80 each are generally rectangularly formed in plan view in astate protruding from the bottoms of the wiring trenches 78, andarranged in the form of a 4 by 4 matrix in plan view as a whole (seeFIG. 4).

The residual dielectric film portions 80 are so arranged in the form ofthe 4 by 4 matrix as a whole that the wiring trenches 78 are arrangedperpendicularly to one another at a prescribed interval to form alattice pattern (5 by 5 in this embodiment). A metallic material(copper, for example) is embedded in the wiring trenches 78, therebyforming metal wires 79. The residual dielectric film portions 80 areexposed from the metal wires 79.

Thus, the residual dielectric film portions 80 are so provided insidethe wiring trenches 78 that the interval between the metal wires 79 canbe reduced between the interlayer dielectric film 77 and the residualdielectric film portions 80 or between the residual dielectric filmportions 80 and the residual dielectric film portions 80 in the row andcolumn directions of the wiring trenches 78.

Among the wiring trenches 78 of the lattice pattern (5 by 5) in theinterlayer dielectric film 77, the central 3 by 3 wiring trenches 78 areprovided with a plurality of interwire connecting via holes 81 passingthrough the interlayer dielectric film 77 from the bottom surfaces ofthe wiring trenches 78 and reaching the metal wires 73. The interwireconnecting via holes 81 are arranged in three lines on each row and eachcolumn along the row and column directions. Thus, the positions of thevertical central axes of the respective substrate connecting via holes75 and the central axes of the respective interwire connecting via holes81 deviate from one another in the direction parallel to the surface ofthe semiconductor substrate 53.

The wiring trenches 78 and the interwire connecting via holes 81communicate with one another. A metallic material (copper, for example)is embedded in the interwire connecting via holes 81, thereby forminginterwire connecting vias 82.

The metal wires 79 are electrically connected with the metal wires 73through the interwire connecting vias 82. In other words, the fourthwiring layer 57 and the third wiring layer 56 are electrically connectedwith each other.

The pad layer 58 is formed on the fourth wiring layer 57. This pad layer58 includes a surface insulating film 83 laminated on the interlayerdielectric film 77. The surface insulating film 83 is made of siliconoxide, for example.

A pad trench 84 generally rectangular in plan view is formed in thesurface insulating film 83 by digging down the surface insulating film83. A metallic material (copper, aluminum or an aluminum-copper alloy,for example) is embedded in the pad trench 84, thereby forming a bondingpad 52.

The surface insulating film 83 is formed with a plurality of padconnecting via holes 85 passing through the surface insulating film 83from the bottom surface of the pad trench 84 and reaching the metalwires 79. The pad connecting via holes 85 are arranged on the samecentral axes as the interwire connecting via holes 75 formed in theinterlayer dielectric film 71. Thus, the positions of the verticalcentral axes of the respective substrate connecting via holes 81 and thecentral axes of the respective pad connecting via holes 85 deviate fromone another in the direction parallel to the surface of thesemiconductor substrate 53.

The pad trench 84 and the pad connecting via holes 85 communicate withone another. A metallic material (copper, aluminum or an aluminum-copperalloy, for example) is embedded in the pad connecting via holes 85,thereby forming pad connecting vias 86 (see FIG. 4).

The bonding pad 52 is electrically connected with the metal wires 79through the pad connecting vias 86. In other words, the pad layer 58 andthe fourth wiring layer 57 are electrically connected with each other.

The semiconductor device 51 is die-bonded to an island of a lead frame(not shown) for a semiconductor package, for example, and the bondingpad 52 is connected to a lead electrode (not shown) of the lead framethrough a bonding wire (not shown) formed by a thin gold wire, forexample, whereby electrical connection between the semiconductor device51 and the external lead frame is attained.

Next, a method of manufacturing the semiconductor device 51 is nowdescribed.

In order to manufacture the semiconductor device 51, the first wiringlayer 54 is first formed on the semiconductor substrate 53.

In this formation of the first wiring layer 54, the interlayerdielectric film 59 is first formed on the semiconductor substrate 53.Then, a photoresist (not shown) patterned correspondingly to thesubstrate connecting via holes 63 is formed on the interlayer dielectricfilm 59. This photoresist is employed as a mask for etching theinterlayer dielectric film 59, thereby forming the substrate connectingvia holes 63 passing through the interlayer dielectric film 59.

Then, the photoresist is removed by ashing, and photoresist patternedcorrespondingly to the wiring trenches 60 is formed on the interlayerdielectric film 59. This photoresist is employed as a mask for etchingthe interlayer dielectric film 59, thereby forming the wiring trenches60 to expose the opening surfaces of the substrate connecting via holes63 and leave the residual dielectric film portions 62.

Then, the photoresist is removed by ashing, and a barrier film (notshown) is deposited by sputtering to cover the upper surface of thesemiconductor substrate 53, the side surfaces of the substrateconnecting via holes 63 and the inner surfaces of the wiring trenches60. After this formation of the barrier film, a metal film (copper film,for example), not shown, is formed on the interlayer dielectric film 59by electrolytic plating, sputtering or CVD, for example, to fill up thesubstrate connecting via holes 63 and the wiring trenches 60.

Then, the metal film is polished by CMP. This polishing is continueduntil the surface of the metal film is flush with that of the interlayerdielectric film 59. Thus, excess parts of the metal film not embedded inthe wiring trenches 60 are removed, and the metal wires 61 embedded inthe wiring trenches 60 are obtained.

Then, the second wiring layer 55 is formed on the first wiring layer 54.

In this formation of the second wiring layer 55, the interlayerdielectric film 65 is first formed on the interlayer dielectric film 59.Then, a photoresist (not shown) patterned correspondingly to theinterwire connecting via holes 69 is formed on the interlayer dielectricfilm 65. This photoresist is employed as a mask for etching theinterlayer dielectric film 65, thereby forming the interwire connectingvia holes 69 passing through the interlayer dielectric film 65.

Then, the photoresist is removed by ashing, and photoresist patternedcorrespondingly to the wiring trenches 66 is formed on the interlayerdielectric film 65. This photoresist is employed as a mask for etchingthe interlayer dielectric film 65, thereby forming the wiring trenches66 to expose the opening surfaces of the interwire connecting via holes69 and leave the residual dielectric film portions 68.

Then, the photoresist is removed by ashing, and a barrier film (notshown) is deposited by sputtering to cover the upper surface of theinterlayer dielectric film 59, the side surfaces of the interwireconnecting via holes 69 and the inner surfaces of the wiring trenches66. After this formation of the barrier film, a metal film is formed onthe interlayer dielectric film 65 by electrolytic plating, sputtering orCVD, for example, to fill up the interwire connecting via holes 69 andthe wiring trenches 66.

Then, the metal film is polished by CMP. This polishing is continueduntil the surface of the metal film is flush with that of the interlayerdielectric film 65. Thus, excess parts of the metal film not embedded inthe wiring trenches 66 are removed, and the metal wires 67 embedded inthe wiring trenches 66 are obtained.

Thereafter, the third wiring layer 56 is formed on the second wiringlayer 55 by a method similar to that for forming the first wiring layer54. Then, the fourth wiring layer 57 is formed on the third wiring layer56 by a method similar to that for forming the second wiring layer 55,thereby completing the multilevel interconnection structure formed bythe respective wiring layers (54, 55, 56 and 57) laminated with oneanother.

After this formation of the fourth wiring layer 57, the pad layer 58 isformed on the fourth wiring layer 57.

In this formation of the pad layer 58, the surface insulating film 83 isfirst formed on the interlayer dielectric film 77. Then, a photoresist(not shown) patterned correspondingly to the pad connecting via holes 85is formed on the surface insulating film 83. This photoresist isemployed as a mask for etching the surface insulating film 83, therebyforming the pad connecting via holes 85 passing through the surfaceinsulating film 83.

Then, the photoresist is removed by ashing, and photoresist patternedcorrespondingly to the pad trench 84 is formed on the surface insulatingfilm 83. This photoresist is employed as a mask for etching the surfaceinsulating film 83, thereby forming the pad trench 84 to expose theopening surfaces of the pad connecting via holes 85.

Then, the photoresist is removed by ashing, and a barrier film (notshown) is deposited by sputtering to cover the upper surface of theinterlayer dielectric film 77, the side surfaces of the pad connectingvia holes 85 and the inner surface of the pad trench 84. After thisformation of the barrier film, a metal film (copper film, aluminum filmor aluminum-copper alloy film, for example) is formed on the surfaceinsulating film 83 by electrolytic plating, sputtering or CVD, forexample, to fill up the pad connecting via holes 85 and the pad trench84.

Then, the metal film is polished by CMP. This polishing is continueduntil the surface of the metal film is flush with that of the surfaceinsulating film 83. Thus, excess parts of the metal film not embedded inthe pad trench 84 are removed and the bonding pad 52 embedded in the padtrench 84 is formed, thereby completing the semiconductor device 51.

In the semiconductor device 51, as described above, the residualdielectric film portions 80 exposed from the metal wires 79 are formedin the fourth wiring layer 57 by partially leaving the interlayerdielectric film 77 in the wiring trenches 78. In the third wiring layer56, the residual dielectric film portions 74 exposed from the metalwires 73 are formed by partially leaving the interlayer dielectric film71 in the wiring trenches 72. In the second wiring layer 55, theresidual dielectric film portions 68 exposed from the metal wires 67 areformed by partially leaving the interlayer dielectric film 65 in thewiring trenches 66. In the first wiring layer 54, further, the residualdielectric film portions 62 exposed from the metal wires 61 are formedby partially leaving the interlayer dielectric film 59 in the wiringtrenches 60.

Thus, the residual dielectric film portions (62, 68, 74 and 80) exposedfrom the metal wires (61, 67, 73 and 79) are so formed inside the wiringtrenches (60, 66, 72 and 78) of the wiring layers (54, 55, 56 and 57)that the interval between the metal wires (61, 67, 73 and 79) can bereduced between the interlayer dielectric films (59, 65, 71 and 77) andthe residual dielectric film portions (62, 68, 74 and 80) or between theresidual dielectric film portions (62, 68, 74 and 80) and the residualdielectric film portions (62, 68, 74 and 80), respectively.

Therefore, the surface areas of the metal wires (61, 67, 73 and 79) canbe reduced as compared with metal wires formed by filling up the wiringtrenches (60, 66, 72 and 78) with copper without providing the residualdielectric film portions (62, 68, 74 and 80) in the wiring trenches (60,66, 72 and 78), respectively.

When the metallic materials are deposited on the interlayer dielectricfilms (59, 65, 72 and 77) formed with the wiring trenches (60, 66, 72and 78) and the residual dielectric film portions (62, 68, 74 and 80)and parts of the metallic materials overflowing the wiring trenches (60,66, 72 and 78) are polished by CMP, respectively, the metal wires (61,67, 73 and 79) each can be prevented from dishing. Consequently,defective resolution in photolithography and a short circuit between thewiring layers can be suppressed, and a semiconductor device having highreliability in quality can be obtained.

The substrate connecting vias 64, the interwire connecting vias 70, theinterwire connecting vias 76, the interwire connecting vias 82 and thepad connecting vias 86 are formed between the semiconductor substrate 53and the first wiring layer 54, between the first and second wiringlayers 54 and 55, between the second and third wiring layers 55 and 56,between the third and fourth wiring layers 56 and 57 and between thefourth wiring layer 57 and the pad layer 58, respectively, whereby thesemiconductor substrate 53, the first to fourth wiring layers 54 to 57and the bonding pad 52 can be electrically connected with one anotherthrough the connecting vias (64, 70, 76, 82 and 86).

The positions of the substrate connecting vias 64 and the interwireconnecting vias 70 deviate from one another in the direction parallel tothe surface of the semiconductor substrate 53. Further, the positions ofthe interwire connecting vias 70 and 76, the interwire connecting vias76 and 82 and the interwire connecting vias 82 and the pad connectingvias 86 also deviate from one another in the direction parallel to thesurface of the semiconductor substrate 53. Thus, the respectiveconnecting vias (64, 70, 76, 82 and 86) connecting the continuous andindividual layers with one another are not aligned with one another butthe positions thereof deviate from one another in the verticaldirection, whereby stress applied to the bonding pad 52 in connectionwith the bonding wire, formation of a bump or probing for a device testcan be dispersed and relaxed. Consequently, the dielectric films (59,65, 71, 77 and 83) each can be inhibited from cracking.

While the second embodiment of the present invention has been described,the present invention can also be embodied in other modes.

For example, the construction in which while the bonding pad 52 is madeof a metallic material such as copper, aluminum or an aluminum-copperalloy, for example, is illustrated in the above-mentioned secondembodiment, the bonding pad 52 may alternatively be constituted of anembedded portion 87 formed by filling up the pad trench 84 with copperand a surface portion 88 made of aluminum arranged on a pad opening 90formed in an insulating film 89 laminated on the surface insulating film83, as shown in FIG. 6.

In order to manufacture the semiconductor device 51 having thisstructure, the pad connecting via holes 85 and the pad trench 84 arefilled up with copper in place of the metallic material (copper,aluminum or an aluminum-copper alloy, for example) in the steps ofmanufacturing the semiconductor device 51 according to theabove-mentioned second embodiment. Thereafter, the copper filling up thepad connecting via holes 85 and the pad trench 84 is polished by CMP.This polishing is continued until the surface of the copper is flushwith that of the surface insulating film 83. Thus, excess parts of thecopper not embedded in the pad trench 84 are removed, and the embeddedportion 87 embedded in the pad trench 84 is formed.

Thereafter, the insulating film 89 is formed on the surface insulatingfilm 83. Then, a photoresist (not shown) patterned correspondingly tothe pad opening 90 is formed on the insulating film 89. This photoresistis employed as a mask for etching the insulating film 89, therebyforming the pad opening 90 passing through the insulating film 89.

Then, the photoresist is removed by ashing, and photoresist (not shown)patterned correspondingly to the surface portion 88 is formed on theinsulating film 89. This photoresist is employed as a mask for formingan aluminum film filling up the pad opening 90 on the region of theinsulating film 89 including the photoresist to cover the embeddedportion 87. Then, the photoresist is dissolved and removed, so that anunnecessary part (other than the surface portion 88) of the aluminumfilm is lifted off along with the photoresist. Thus, the surface portion88 is so formed as to form the bonding pad 52 including the embeddedportion 87 and the surface.

An aluminum-copper alloy may be employed as the material of the surfaceportion 88 in place of aluminum in the above-mentioned modification.

While the residual dielectric film portions (62, 68, 74 and 80) each aregenerally rectangularly formed in plan view in the above-mentionedsecond embodiment, the residual dielectric film portions (62, 68, 74 and80) may alternatively be circularly or triangularly formed in plan view,for example.

While the metal wires (61, 67, 73 and 79) each are made of copper in theabove-mentioned second embodiment, the metal wires (61, 67, 73 and 79)each may alternatively be made of another metal.

While the metal wires (61, 67, 73 and 79) each are formed by theso-called dual damascene process in the above-mentioned secondembodiment, the metal wires (61, 67, 73 and 79) may alternatively beformed by the so-called single damascene process.

While the illustrative embodiments of the present invention aredescribed in detail, these are mere specific examples for clarifying thetechnical contents of the present invention and it is not to beconstrued limitative thereto. The spirit and the scope of the inventionare only limited by the claims appended hereto.

1. A semiconductor device comprising: a semiconductor substrate; awiring layer laminated on the semiconductor substrate; a surfaceinsulating layer laminated on the wiring layer; and a bonding padembedded in a surface of the surface insulating layer and connected witha bonding wire for external electrical connection, wherein the wiringlayer comprises: an insulating layer; a residual insulating layerportion formed by partially leaving the insulating layer in a wiringtrench formed by digging down the insulating layer; and a metal wiringpattern formed by embedding a metallic material in the wiring trench andelectrically connected with the bonding pad.
 2. The semiconductor deviceaccording to claim 1, wherein the wiring layer includes at least firstand second wiring layers, the semiconductor device further comprising: abonding pad connecting via formed through the surface insulating layerfor connecting the metal wire of the first wiring layer and the bondingpad with each other; and a metal wire connecting via formed through theinsulating layer of the first wiring layer for connecting the metal wireof the first wiring layer and the metal wire of the second wiring layerwith each other.
 3. The semiconductor device according to claim 2,wherein the bonding pad connecting via and the metal wire connecting viaare so formed that positions in a direction parallel to a surface of thesemiconductor substrate deviate from each other.